Grassy St John's Wort

Cultivating Grassy St John's Wort (Hypericum gramineum) is a rewarding endeavor for any gardener interested in New Zealand's unique flora. This species can be propagated through several methods, each requiring specific conditions to ensure healthy growth and establishment. Successful propagation depends on mimicking the plant's natural environment and providing consistent care during the early stages of development. It is an adaptable plant that can add charm to rockeries and open spaces.

From Seed

Propagation from seed is often the most effective way to produce a large number of Grassy St John's Wort plants. Seeds should be collected when the capsules turn brown and begin to split, usually in late summer or autumn. Freshly collected seeds generally have higher germination rates than those that have been stored for long periods.

To grow from seed:

1. Prepare a seed-raising mix that is free-draining, such as a blend of potting mix and sand or perlite.
2. Sow the fine seeds on the surface of the mix. Do not cover them deeply, as they require some light to germinate; a very light dusting of sand is sufficient.
3. Water the tray gently using a fine mist to avoid displacing the seeds.
4. Place the tray in a warm, well-lit area, but out of direct scorching sun. Maintain a temperature of around 18-20°C.
5. Keep the medium consistently moist but not waterlogged. Germination can be irregular, taking anywhere from a few weeks to a couple of months.
6. Once seedlings have developed their second pair of true leaves and are large enough to handle, prick them out into individual small pots.
7. Harden off the young plants gradually before planting them out into their final position in the garden.

Seedlings may self-sow in the garden if conditions are favorable, providing a natural renewal of plants.

From Cuttings

For those wishing to replicate specific characteristics of a parent plant, vegetative propagation via cuttings is the preferred method. This technique ensures that the new plants are genetically identical to the source. Softwood cuttings taken during the spring or early summer usually yield the best results for this species.

To propagate from cuttings:

1. Select healthy, non-flowering shoots that are approximately 5-10 cm long.
2. Using a sharp, clean knife or secateurs, make a clean cut just below a node (the point where leaves attach to the stem).
3. Remove the lower leaves from the bottom third of the cutting to expose the nodes.
4. Dip the cut end into rooting hormone powder or gel to encourage root development and prevent rot.
5. Insert the cuttings into a pot filled with a gritty, free-draining propagation mix, such as coarse sand and peat.
6. Place the pot in a humid environment, such as a propagator or inside a plastic bag, and keep it in bright, indirect light.
7. Mist the cuttings regularly to maintain humidity. Roots should develop within a few weeks.
8. Once rooted, pot the cuttings up individually and grow them on until they are established enough to be planted out.

Additional Methods

Depending on the growth habit of Grassy St John's Wort, division can also be a viable option for established clumps. This is best done in early spring or autumn when the plant is not in active flower.

To divide plants:

1. Carefully lift the plant from the ground or pot, taking care not to damage the root system excessively.
2. Gently tease the roots apart to separate the clump into smaller sections, ensuring each section has both roots and shoots.
3. Replant the divisions immediately into prepared soil or pots and water well to settle them in.